Electrical meter



March 21, 1933. I w MEANS 1,901,921

ELECTRICAL METER Filed May 24, 1930 W J MEANS Patented Mar. 21, 1933 UNITED STATES PATENT OFFICE 'WIDTTHROP J. MEANS, OF BROOKLYN, NEW YORK, ASSIGNOR TO BELL TELEPHONE LABORATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION 01* NEW YORK ELECTRICAL METER Application filed May 24,

This invention relates to electrical meters and particularly to recording meters for permanentl recording electrical variations.

In accor ance with one method of producing a record a heat sensitive paper strip is moved forward at a uniform rate of speed over a suitable guide member which is directly under a heated stylus. The heat from the stylus affects the paper thereby producing a distinguishing mark upon the paper which records the relative movement of the stylus and the sheet. Such devices however are not entirely satisfactory since the guide member over which the paper asses even when made of material having ow thermal conductivity such as wood, absorbs a large portion of the heat directed on the paper thus increasing the heat required to produce a legible record and decreasing the definition obtained.

In accordance with the present invention the amount of heat required is reduced to a minimum and a clearer record obtained by making the guide member over which the record sheet passes from material having high thermal conductivity properties and by providing an air space in that portion of the guide member over which the .heated stylus passes.

When the record sheet is drawn over this type of guide member only that portion of the sheet immediately over the an space is affected b the heat from the stylus. The portion 0 the record sheet passing at any moment over the remaining part of the ide member remains unaffected due to the heat conducting properties of the guide member. This corresponds to the optimum condition of drawing the record sheet over a straight edge of air.

A clearerunderstanding of this invention may be had by reference to the accompanying drawing in which Fig. 1 is a schematic view of the apparatus embodying this invention and Fig. 2 is a plan view of such apparatus.

Referring to the drawing a record sheet or strip of heat sensitive flexible material 11 is shown passing from a supply reel 10 over aguide member 12 and between a 1830. Serial No. 455,272.

guide roller 13 and a toothed roller 14. This sheet is adapted to be moved forward in the direction of the arrow under the influence of roller 14, the teeth of which mesh with the perforations along the edge of sheet 11 so that an elemental section becomes progressively exposed over the slot 15 in guide member 12. One type of record sheet which may be employed comprises a fat or wax coated paper. The action of heat in this case is to melt the wax thus leaving a translucent line, the legibility of which can be intensified by the use of a suitably colored paper base. Papers of this sort may be prepared in a number of ways as, for example, by spraying with a fatty solution. The essential feature of such papers is that the wax or fat is in. a finely divided state on the surface of the paper and is opaque until melted. Another type of record sheet which may be employed comprises the combination of a suitably colored wax paper placed face to face with a thin white absorbent paper. The action of heat in this case is to melt the colored wax coating on the paper which coating is absorbed by the white paper, thus giving a clear sharp edged record. It is to be understood, however, that other chemically treated apers or tapes may equally well be emp oyed, the essential feature being that such papers or tapes become discolored when heat of a proper and predetermined temperature is ap lied.

moving coil 18 wound on core 16 is placed between the poleieces N and S of a permanent magnet 17 w ich magnet maintains a strong magnetic field. The movable secondary 27 of a transformer is securely fastened to core 16 on which the coil 18 is wound, the core 16 and the secondary 27 being pivoted at points 29 and 30. Hence when the electrical variations which are to be recorded are impressed upon the leads L connected to the moving coil 18, the coil is deflected in proportion to these electrical variations and a pointer which is rigidly secured to the movable secondary 27 and which comprises two conductors 19 and 20 and a resistance wire 21, is deflected accordingly. Conductors 19 and 20 may, for example, be ordinary conductors, such as copper wires and are held in spaced relation by means of insulating spacers 22 and 23. The resistance wire 21, however, is made of a metal which becomes heated to a comparatively hi h temperature by suitable current passing erethrough. This current is supplied by any suitab e source such as the generator 24, through the medium of a transformer which com rises a stationary primary 26 and the cell 27 which functions as a movable secondary. In operation the switch 25 is closed, thus permitting the passage of current from generator 2 through stationary prima 26 from where it is 1nductively conveye to the movable secondary 27 and thence through the resistance wire 21. The stationary primary 26 is arranged to be symmetrical with respect to the axis of rotation of coil 18 and movable secondar 27 in which case, the stationary rimarywi remain unafiected by the angu ar position of the pointer and will exert no torque on the moving system. Resistance wire 21 is of suflicient length so that a ortion thereof will always be adjacent to e exposed elemental section of sheet 11. Thus when the pointer moves through the arc of a circle corresponding to the distance between the edges of the sheet, a portion of the resistance wire 21 will be opposite to and almost in contact with a portion of the elemental section of sheet 11. The minimum distance between the heat sensitive sheet and the resistance wire 21 is determined principslly by the temperature at which the sheet actions to give a suitable indication.

To prevent the guide rod 12 from absorbing heat which if permitted would cause a blurring of the record as well as an increase in the amount of heat r uired, this guide rod is made of a metal aving high heat conducting properties, such as co per, and is provided with a longitudinal s ot 15 on the portion adjacent the resistance wire. When the heat sensitive sheet is drawn over this type of guide member, only that portion over the slot and hence with air behind it produces a record. The portion passing over the metal base is unaffected due to the heat conducting properties of the bar. This corresponds to the optimum position of drawing the paper over a straight edge of air.

Thus, the apparatus disclosed herein provides a system in which a heat sensitive flexible material is moved, so that an elemental section thereof becomes exposed to a source of heat, said source of heat moving from one edge of the flexible material to the other in accordance with the electrical variations, the heat of the source causing a permanent impression on the flexible material. The

record thus produced on the flexible material is continuous rather than intermittent. The electrical variations may be recorded by such apparatus at a speed depending upon time required in having the heat sensitive sheet undergo a permanent change.

While this invention has been pointed out in a particular embodiment merely for the purpose of illustration, it is to be understood that the general principle of this invention may be applied to other and widely varied indicating and recording instruments without departing from the spirit of the invention.

What is claimed is:

1. The method of recording electrical variations which consists in transmittin a strip of heat sensitive material over a guide member having a longitudinal slot so that a narrow sectlon of said material becomes progressively exposed over the slot and app ying heat steadily to the exposed narrow section to cause a permanent impression upon said material.

2. The method of recording electrical variations which consists in transmitting a strip of heat sensitive material over a guide member so that a narrow section of the paper becomes progressively exposed over a slot in the 1de member, applying heat to the expose narrow section and changin the point of application of the heat. wit respect to the edges of said material in accordance with electrical variations whereby a permanent record of these electrical variations will. be established on said paper.

3. A recording meter comprising a strip of heat sensitive material a su porting member having a longitudinal s ot over which said strip traverses, means for assing said strip over said slot at a uni orm rate of speed and means for ap lying heat to that portion of the strip immediately over said slot.

4. A recording meter comprising a strip of heat sensitive material, a supportin member of high heat conducting materiad having a longitudinal slot therein over which said strip traverses, a source of heat adjacent said strip and means for movin said source of heat between the edges 0 said strip whereby a permanent record may be made of the variations in the characteristics of an electrical source.

5. A recording meter com rising a strip of heat sensitive material, a reater element including a stationary coil and a movable coil inductively coupled together and means for progressively ex osing an elemental section of said materia to said heater element.

6. A recording meter comprising a strip of heat sensitive material, a guide member of high thermal conductivity having a longitudinal slot therein, means for progressively exposing an elemental section of said material over said slot, a heater element adjacent said exposed sect'on, means including a stationary primar and a movable secondary inductively coup ed together for heating said element, and means including said secondar for moving said heater element over sai exposed section in accordance with electrical variations.

In Witness whereof, I hereunto subscribe my name this 23rd day of May, 1930.

WINTHROP J. MEANS. 

